The present invention relates to a material for a fluorine-containing coating composition, a primer for a fluorine-containing coating composition, an aqueous dispersion for a fluorine-containing coating composition, a fluorine-containing powder coating composition and a resin composition for a fluorine-containing coating composition which can be firmly adhered to substrates such as metal, glass, etc. when coating the substrate with a fluorine-containing polymer, and a method for coating a surface of a substrate with a fluorine-containing polymer by using the primer for a fluorine-containing coating composition.
A a fluorine-containing polymer has been preferably used as a coating material applied to a surface of metal because of its excellent characteristics such as chemical resistance, thermal resistance and non-sticking property, and is used, for example, for lining of chemical apparatuses requiring corrosion resistance, inner lining of cooking apparatuses such as a rice cooker requiring corrosion resistance and non-sticking property, and other applications. However since its adhesion to a surface of metal is not sufficient due to its excellent non-sticking property, hitherto various modifications have been made to improve adhesion to the surface of metal.
One of them is a method for adhering a fluorine-containing polymer to a substrate by roughening the surface of metal chemically or physically with expecting an xe2x80x9canchor effectxe2x80x9d therebetween. In this method, the surface roughening itself requires much labor, and though initial adhesion is possible, lowering of the anchor effect arises at the time of temperature change and at high temperature.
Also a method for chemically activating a surface of a fluorine-containing resin by treating the surface with a solution prepared by dissolving metallic sodium in liquid ammonia has been proposed. However in this method, not only there was a fear that the solution itself causes environmental pollution but also there was a problem that its handling is attended with danger. Further, there have been proposed methods for carrying out physical and chemical treatment such as plasma sputtering on a surface of a fluorine-containing resin or mechanically roughening the surface of a fluorine-containing resin. However these methods have problems such that the mentioned treatments require much labor, increase in cost arises and design or appearance of a coated surface is injured.
Also in order to improve adhesion of a fluorine-containing coating, investigations with respect to addition of various components and use of a primer have been made.
For example, there is a technique of adding an inorganic acid such as chromic acid to a coating composition containing a fluorine-containing polymer to form a chemical conversion coating film on a surface of metal for enhancing adhesion of the composition (JP-B-63-2675). However since chromic acid contains hexahydric chromium, it can be said that such a technique is not sufficient in view of safety in food and coating work. Further in case of use of other inorganic acids such as phosphoric acid, there was a problem such that safety of a fluorine-containing resin coating composition is damaged.
Use of a coating composition containing a fluorine-containing resin as a primer, in which heat resistant resins such as polyamideimide, polyimide, polyethersulfone and PEEK and in addition, a metal powder are added instead of the above-mentioned inorganic acid, has been studied (JP-A-6-264000). Inherently there is no compatibility between a fluorine-containing polymer and heat resistant resin. Therefore there arises a phase separation in a coating film, thus easily causing intercoat adhesion failure between the primer and the top coat. Further, film defects such as pin holes and cracks arise easily at the time of processing at high temperature and during use due to difference in heat shrinkage between the fluorine-containing resin and the heat resistant resin or due to lowering of elongation of the coating film by the addition of the heat resistant resin. Also since these heat resistant resins are colored brown by baking, it is difficult to use them for applications requiring white and vivid colors and transparency.
Further, non-sticking property and low friction property which the fluorine-containing resin inherently possesses are lowered.
Also for adhesion of a fluorine-containing resin coating composition to a glass requiring transparency, improvements of the adhesion have been tried by treating the substrate with a silane coupling agent or adding a silicone resin to the fluorine-containing resin coating composition (JP-B-54-42366, JP-A-5-177768, etc.). However thermal resistance and adhesion are insufficient, and separation of film, foaming and coloring arise easily at high temperature.
On the contrary, fluorine-containing coating compositions prepared by copolymerizing a hydrocarbon monomer containing a functional group such as hydroxyl or carboxyl have been discussed. However those coating compositions were originally studied mainly for a purpose of weather resistance, and therefore it is difficult to use them for applications requiring thermal resistance at 200xc2x0 to 350xc2x0 C. which is directed by the present invention, and for applications requiring non-sticking property, low friction property, etc.
Namely with respect to a polymer prepared by copolymerizing a hydrocarbon monomer (containing no fluorine) having a functional group, thermal decomposition easily occurs on components of the monomer at the time of processing at high temperature or during use, and thus coating film failure, coloring, foaming, separation, etc. arise, which makes it impossible to attain purposes of coating a fluorine-containing resin.
An object of the present invention is to solve the above-mentioned problems, and to provide a material for fluorine-containing coating composition which maintains excellent characteristics such as thermal resistance, chemical resistance, non-sticking property and low friction property of fluorine-containing polymer and further can have strong adhesion directly to a substrate such as metal, glass, etc., and to provide a method for coating by using the material for coating compositions.
The present invention relates to a material for a fluorine-containing coating composition which comprises a fluorine-containing ethylenic polymer having a functional group and prepared by copolymerizing:
(a-1) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of functional groups selected from hydroxyl, carboxyl, carboxylate salt group, carboxylate ester group or epoxy and
(b-1) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers which do not have the functional group mentioned above.
Further the present invention relates to a primer for a fluorine-containing coating composition which comprises a fluorine-containing ethylenic polymer having a functional group and prepared by copolymerizing:
(a-2) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of functional groups selected from hydroxyl, carboxyl, carboxylate salt group, carboxylate ester group or epoxy and
(b-2) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers which do not have the functional group mentioned above.
Further the present invention relates to an aqueous dispersion for a fluorine-containing coating composition which comprises a fluorine-containing ethylenic polymer having a functional group and prepared by copolymerizing:
(a-3) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of functional groups selected from hydroxyl, carboxyl, carboxylate salt group, carboxylate ester group or epoxy and
(b-3) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers which do not have the functional group mentioned above.
Further the present invention relates to a fluorine-containing powder coating composition which comprises a fluorine-containing ethylenic polymer having functional group and prepared by copolymerizing:
(a-4) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of functional group selected from hydroxyl, carboxyl, carboxylate salt group, carboxylate ester groups or epoxy and
(b-4) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers which do not have the functional group mentioned above.
In the present invention, it is preferable that the above-mentioned fluorine-containing ethylenic monomer (a-1) having functional a group is a fluorine-containing ethylenic monomer having a hydroxyl group.
It is also preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (a-1) having a functional group is at least one of monomers represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94Yxe2x80x83xe2x80x83(1)
wherein Y is xe2x80x94CH2OH, xe2x80x94COOH, carboxylate salt group, carboxylate ester group or epoxy, X and X1 are the same or different and each is hydrogen atom or fluorine atom, Rf is a divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having an ether bond and 1 to 40 carbon atoms.
It is also preferable in the present invention that in the above-mentioned formula (1), Y is xe2x80x94CH2OH.
It is further preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (a-1) having a functional group is a fluorine-containing monomer represented by the formula (2):
CH2xe2x95x90CFCF2xe2x80x94Rf1xe2x80x94Y1xe2x80x83xe2x80x83(2)
wherein Y1 is xe2x80x94CH2OH, xe2x80x94COOH, carboxylate salt group, carboxylate ester group or epoxy, Rf1 is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms or xe2x80x94ORf2, in which Rf2 is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms or a divalent fluorine-containing alkylene group having a ether bond and 1 to 39 carbon atoms.
It is preferable in the present invention that the fluorine-containing ethylenic monomer (b-1) having no functional group mentioned above is tetrafluoroethylene.
It is preferable in the present invention that the fluorine-containing ethylenic monomer (b-1) having no functional group mentioned above is a monomer mixture of 85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of a monomer represented by the formula (3):
CF2xe2x95x90CFxe2x80x94Rf3xe2x80x83xe2x80x83(3)
wherein Rf3 is xe2x80x94CF3 or ORf4, in which Rf4 is a perfluoroalkyl group having 1 to 5 carbon atoms.
It is preferable in the present invention that the fluorine-containing ethylenic monomer (b-1) having no functional group mentioned above is a monomer mixture of 40 to 80% by mole of tetrafluoroethylene or chlorotrifluoroethylene, 20 to 60% by mole of ethylene and 0 to 15% by mole of other monomer copolymerizable therewith.
Further the present invention relates to a resin composition for a fluorine-containing coating composition which comprises:
(A-1) 1 to 90% by weight of a fluorine-containing ethylenic polymer having functional a group and prepared by copolymerizing:
(a-5) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of functional groups selected from hydroxyl, carboxyl, carboxylate salt group, carboxylate ester group or epoxy and
(b-5) 70 to 99.95% by mole. of at least one of fluorine-containing ethylenic monomers having no functional group mentioned above, and
(B-1) 10 to 99% by weight of a fluorine-containing ethylenic polymer having no functional group in its branched chain.
In the present invention, it is preferable that the above-mentioned fluorine-containing ethylenic polymer (A-1) having a functional group is at least one of fluorine-containing ethylenic polymers having a functional group such as
a copolymer comprising (a-5) at least one of fluorine-containing ethylenic monomers having functional group and represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94Yxe2x80x83xe2x80x83(1)
xe2x80x83wherein Y represents xe2x80x94CH2OH, xe2x80x94COOH, carboxylate salt group, carboxylate ester group or epoxy, X and X1 are the same or different and each is hydrogen atom or fluorine atom, Rf is a divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having an ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having an ether bond and 1 to 40 carbon atoms, and (b-5) tetrafluoroethylene, and
a copolymer comprising the above-mentioned fluorine-containing monomer (a-5) having a functional group and as the component (b-5), a monomer mixture of 85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of a monomer represented by the formula (3):
CF2xe2x95x90CFxe2x80x94Rf3xe2x80x83xe2x80x83(3)
xe2x80x83wherein Rf3 is xe2x80x94CF3 or ORf4, in which Rf4 is a perfluoroalkyl group having 1 to 5 carbon atoms, based on the total amount of the monomers except the component (a-5), and that
(B-1) is at least one of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer or tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer.
Further the present invention relates to the method for coating a surface of substrate with a fluorine-containing polymer, which comprises: forming, on the substrate, a layer of a primer for a fluorine-containing coating composition which comprises a fluorine-containing ethylenic polymer (A-2) having a functional group and prepared by copolymerizing
(a-2) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having any one of hydroxyl, carboxyl, carboxylate salt group, carboxylate ester group or epoxy and
(b-2) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers having no functional group; forming, on the formed primer layer, a layer of a fluorine-containing ethylenic polymer (B-1) having no functional group in its branched chain; and then
sintering the primer layer and the layer of the fluorine-containing ethylenic polymer having no functional group in its branched chain.
Further in the present invention, it is preferable that the above-mentioned primer (A-2) for a fluorine-containing coating composition is at least one of fluorine-containing ethylenic polymers having a functional group such as
a copolymer comprising (a-2) at least one of the fluorine-containing ethylenic monomer having a functional group and represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94Yxe2x80x83xe2x80x83(1)
xe2x80x83wherein Y represents xe2x80x94CH2OH, xe2x80x94COOH, carboxylate salt 5group, carboxylate ester group or epoxy, X and X1 are the same or different and each is hydrogen atom or fluorine atom, Rf is a divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having ether bond and 1 to 40 carbon atoms, and
(b-2) tetrafluoroethylene, and
a copolymer comprising (a-2) the above-mentioned fluorine-containing monomer having a functional group and as the component (b-2), a monomer mixture of 85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of a monomer represented by the formula (3):
CF2xe2x95x90CFxe2x80x94Rf3xe2x80x83xe2x80x83(3)
xe2x80x83wherein Rf3 is xe2x80x94CF3 or ORf4, in which Rf4 is a perfluoroalkyl group having 1 to 5 carbon atoms, based on the total amount of the monomers except the component (a-2), and that
(B-2) is at least one of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer or tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer.
Further it is preferable in the present invention that the surface of a substrate to be coated with the above-mentioned fluorine-containing polymer is a metal surface.
Further the present invention relates to the method for coating the surface of glass substrate with any of the above-mentioned fluorine-containing polymers.